KSI-501 is a novel anti-VEGF and anti-IL-6 bispecific biopolymer conjugate to simultaneously address neovascularization and inflammation in retinal diseases

Abstract

Purpose : Neovascularization and inflammation play major roles in the pathogenesis of retinal diseases. While monospecific anti-VEGF therapies have been proven to treat neovascularization effectively, they do not address the underlying immune component. Elevated intraocular levels of IL-6 have been implicated in diabetic eye diseases and linked to anti-VEGF treatment resistance in age-related macular degeneration (AMD). We designed KSI-501, a novel VEGF-trap anti-IL-6 bispecific protein conjugated with a high molecular weight biopolymer, which inhibits both signaling pathways with expected long durability.

Methods : A trap-antibody fusion protein was engineered to bind and inhibit both IL-6 and VEGF with the capability of being conjugated to a high molecular weight phosphorylcholine-based biopolymer. Binding affinity and biological activity were investigated using surface plasmon resonance (SPR), Kinetic Exclusion Assay (KinExA), enzyme-linked immunosorbent assay (ELISA), and cell-based assays. Size exclusion chromatography with multi-angle static light scattering (SEC-MALS) and SDS-PAGE were used to determine the antibody:biopolymer conjugation stoichiometry. Negative staining electron microscopy (EM) was used to visualize the VEGF-trap and VEGF complex interaction.

Results : The VEGF-trap anti-IL-6 molecule exhibits high binding affinities to VEGF-A isoforms, VEGF-B, PlGF, PlGF-2, and IL-6. In addition, binding studies show the bispecific molecular design allows for drug engagement with VEGF and IL-6 in an independent and simultaneous manner. Functional assays show the drug inhibits interactions between targets and their respective receptors. KSI-501 exhibits a 1:1 antibody:biopolymer conjugation ratio as supported by SEC-MALS and SDS-PAGE. EM 2D class averaging shows KSI-501 establishes a 1:1 complex with VEGF in which both trap arms engage one VEGF molecule.

Conclusions : KSI-501 has high binding affinity and bioactivity against VEGF and IL-6. Thereby it has the potential to synergistically inhibit both neovascularization and inflammation components underlying the pathogenesis of retinal diseases. Combined with the ABC platform™ which confers enhanced retinal durability, KSI-501 is a promising long-durability therapeutic candidate for vascular and inflammatory diseases.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.